Introversion and extraversion constitute the foundational attitudinal polarity of Jung’s typological system, first systematically elaborated in Psychological Types (1921) and subsequently amplified, contested, and refined across the entire depth-psychological literature. Jung defined extraversion as the orientation of psychic energy toward the object and the external world, introversion as the orientation toward the subject and the inner world — a distinction he traced to observable differences in the theoretical presuppositions of Freud and Adler. The corpus reveals several productive tensions around this pairing. First, there is the question of balance versus dominance: Jung and his commentators consistently warn against perfect equilibrium, arguing that a habitual one-sided attitude is the condition of psychological development, while also acknowledging that excessive one-sidedness courts neurosis and compensatory eruption of the inferior attitude. Second, the relationship between attitude and function-type generates ongoing complexity: the eight function-attitudes (extraverted thinking, introverted feeling, and so forth) ramify the simple binary into a rich typological grammar. Third, later voices — von Franz, Beebe, Thomson, Quenk — attend to the pathology of the inferior attitude, noting that when introverts are seized by extraversion, or extraverts by introversion, the result is characteristically barbaric and uncontrolled. The term has entered popular language while retaining its technical depth in analytical psychology, where it remains inseparable from questions of individuation, shadow, anima/animus, and the self-regulatory dynamics of the psyche.